Photoelectron Spectromicroscopy and Coherent Xray Microscopy

1

• Photoelectron Spectromicroscopy -- and Coherent
  X-ray Microscopy

Giorgio Margaritondo Dean, School of Basic
Sciences EPF-Lausanne
2

• The brightness of a light source

3

• The historical growth in brightness/brilliance
• (units photons/mm2/s/mrad2, 0.1 bandwidth)

4

• Photoelectron spectroscopy basic ideas

The photon absorption increases the electron
energy by hn before ejection of the electron from
the solid
5

• Photoelectron spectroscopy of
• high-temperature superconductivity

6

• Superconducting gap spectroscopy

7

• From spectroscopy to spectromicroscopy

Spectroscopy (energy and momentum resolution)
Microscopy (spatial resolution)
8

• The first mode of photoemission
  spectromicroscopy scanning spectromicroscopy

9

• The second mode of photoemission
  spectromicroscopy electron-imaging
  spectromicroscopy

10

• The ESCA Microscopy Beamline at ELETTRA

11

• Inhomogeneous chemical reactions at the
  unreactive (!) Gase-Ge interface (J. Almeida et
  al.)

12

• Inhomogeneous and thickness-dependent chemical
  reactions at the unreactive (!) Gase-Si
  interface

13

• Early Results on BCSCO (Y. Hwu et al., Nucl.
  Instrum. Meth. A361, 349 (1995)

The intensity of the photoemission (yield) Sr
signal from cleaved BCSCO changes significantly
from place to place
14

• Photoemission Spectromicroscopy Applied to
  Cleaved BCSCO M. Bertolo, S. La Rosa et al.,
  Phys, Rev. B 66, 060506R (2002)

15

• Photoelectron spectromicroscopy (on untreated
  specimens) beats optical microscopy staining in
  revealing cell nuclei
• (B. Gilbert , M. Neumann , S. Steen , D. Gabel ,
  R. Andres, P. Perfetti, G. Margaritondo and
  Gelsomina De Stasio)

16

• Photoelectron spectromicroscopy explores fine
  chemical details in boron uptake in cells, in
  preparation for neutron cancer therapy
• (B. Gilbert , Gelsomina De Stasio et al.)

17

• Coherent X-ray Imaging and Microscopy

18

• Coherence the property that enables a wave to
  produce visible diffraction and interference
  effects

The diffraction pattern may or may not be visible
on the fluorescent screen depending on the source
size x, on its angular divergence q and on its
wavelength bandwidth Dl
19

• Condition to see the pattern Dl/l lt 1
• Parameter characterizing the longitudinal
  coherence coherence length Lc l2/Dl
• Condition of longitudinal coherence Lc gt l

20

• Lateral (space) coherence analyzed with a
  source formed by two point sources

• Two point sources produce overlapping patterns
  diffraction effects are no longer visible.

• However, if the two source are close to each
  other an overall diffraction pattern may still be
  visible the condition is to have a large
  coherent power (2l/xq)2

21

• Coherence summary

• Large coherence length Lc l2/Dl
• Large coherent power (2l/xq)2
• Both difficult to achieve for small wavelengths
  (x-rays)
• The conditions for large coherent power are
  equivalent to the geometric conditions for high
  brightness

22

• Conventional (Absorption) Radiology

23

• Some Problems in Conventional Radiology

24

• Light-matter Interactions

For over one century, radiology was based on
absorption why not on refraction /diffraction?
25
(No Transcript)
26

• Refraction x-ray imaging

27

• Refraction x-ray imaging -- potential
  advantages over absorption

• Differences between different objects small in
  both cases, but larger for n than for a
• This phenomenon becomes more relevant as the
  wavelength decreases
• Better edge visibility can lead to better
  contrast with a smaller dose

28
(No Transcript)
29
(No Transcript)
30

• Refractive-index radiology of a mouse kidney
• Y. Hwu, W. L. Tsai J. H. Je, A. Groso, G.
  Margaritondo et al.

31

• Refractive-index radiology of a mouse liver

32

• Refractive-index radiology of a firefly

33

• Very Early Detection of Human Liver Cancer
• Yongpeng Tong, Guilin Zhang, Yan Li (Shanghai
  Inst. Of Nuclear Research), Yeukuang Hwu, Wen-Li
  Tsai, Pei-Chebg Hsu, (Academia Sinica Taipei),
  Jung Ho Je (POSTECH), G. Margaritondo (EPFL),
  Dong Yuan (Shanghai CDC)

34

• Very Early Detection of Human Liver Cancer
• Yongpeng Tong, Guilin Zhang, Yan Li (Shanghai
  Inst. Of Nuclear Research), Yeukuang Hwu, Wen-Li
  Tsai, Pei-Chebg Hsu, (Academia Sinica Taipei),
  Jung Ho Je (POSTECH), G. Margaritondo (EPFL),
  Dong Yuan (Shanghai CDC)

35

• A bit more sophisticated description

Small collimated
In the actual image, each edge is marked by
fringes produced by Fresnel edge diffraction. The
fringes enhance the edge and carry holographic
information
36

• Modeling interplay of refraction and
  diffraction

37

• Modeling conditions for coherence-based
  radiology

Conditions to see the edge diffraction
fringes x lt 0.8 D v(l/2L) 100 micron Dl/l lt
v2 Equivalent condition for refraction
radiology x/D lt q
38

• Examples of refraction radiology

39

• Building on bubbles

40

• Opening of a stoma

41

• Phase -contrast tomography

42

• Coherent x-ray tomography

raw microradiograph (one of the many taken in
different directions)
Reconstructed (differential) tomography images
43

• New types of sources
• Ultrabright storage rings (SLS, new Grenoble
  project) approaching the diffraction limit
• Self-amplified spontaneous emission (SASE) X-ray
  free electron lasers
• VUV FELs (such as CLIO)
• Energy-recovery machines
• Inverse-Compton-scattering table-top sources

44

• Free-electron lasers

45

• The scanning near-field optical
• microscope (SNOM) like the stethoscope

SNOM resolution well below the diffraction
limit of standard microscopy ( l)
46

• 20x20 µm2 SNOM image of growth medium (A.
  Cricenti et al.)

47

• Self-amplified spontaneous emission x-ray
  free-electron lasers (SASE X-FELs)

Normal (visible, IR, UV) lasers
SASE strategy
electron bunch
48

• Seeding-Amplifier X-FELs

Electron Beam Bypass
Electron Dump
49

• SASE x-ray FELs

50
(No Transcript)